It is now up to 20,000 miles with the first generation 987. This is called extended drain intervals. You can read about it here. Other car companies are doing this as well.
http://www.bobistheoilguy.com/forums/ubbthreads.php
I am from the old school where it was about 6,000 miles. But I go over it. Engines have improved over the years. Other cars hold about 4 to 5 quarts and use normal oil. The Boxster holds almost 10 quarts and uses synthetic. So I go it out of my mind and change the oil every 15,000 miles, if it needs it or not. I do not do anything fancy with the car - it is my daily driver and only car.
I have a 1997 that I have owned for 9 years with 67,000 miles.